Teacher tenure is often criticized, in that it lets bad or unfit teachers remain in employment. Teacher tenure is not only an expensive system, it allows bad teachers to remain employed, simply because they can not be fired.
Tenure is a system that not only allows bad teachers to negatively influence many students, it is also extremely expensive for the school. A district which is forced to pay unqualified, tenured teachers, will not only have its students suffer, it will also be unable to use that funding for more important purposes, such as hiring more qualified, experienced teachers, or paying for materials and upgrades to infrastructure. Though many tenured teachers are great teachers who definitely deserve to remain in employment, there are also others who remain teachers simply due to tenure.
Though teaching is an important job which requires some degree of stability, no job should have the lack of accountability which tenure provides. Tenure is a process that harms both the district and the individual student, and should be used minimally.